Avamar: Client performance and Windows NTFS compression

A customer is planning on using NTFS (file system level) compression. They would like to know how Avamar handles this or what impact to expect on backup behavior or performance.

NTFS compression operates transparently to the software running on top of NTFS compressed volumes.

When Avamar attempts to read an NTFS compressed file or directory, the operating system presents that file or directory to Avamar in an uncompressed format. 

This process is transparent but there is a performance overhead as Windows performs decompression and recompression of the data in the background.

An Avamar backup is I/O read intensive. NTFS compression overhead may cause backups to run more slowly compared with an identical file system which does not use NTFS compression.

For further information, see Microsoft article #251186: "Best practices for NTFS compression in Windows"